The scanning drive mechanism of the spaceborne microwave-sounding antenna has two working modes of constant speed and variable speed, and the special structural form and layout of the reflecting surface lead to a large perturbation moment in the constant speed and variable speed scanning modes. The optimized design of the reflecting surface reinforcement structure of the antenna’s scanning drive mechanism is of great significance for the adjustment of the dynamic stiffness and rotational moment of inertia of the system, which helps to reduce the influence of the moment perturbation. In this paper, a design method combining topology optimization and size optimization is adopted to optimize the design of the reflecting surface reinforcement structure of the planar antenna. The topology optimization constrains the volume, and the objective function is the first-order frequency maximum. The topology optimization results show that the reinforcement is arranged along the center in a “palm” shape. The size optimization is based on the objective of minimizing the rotational inertia of the structure, and the constraints are the dynamic stiffness and the RMS of the structural stress values. The dynamic stiffness of the structure is improved after size optimization, the mass of the reinforcing bar is reduced by 26% compared with the original structure, the rotational inertia of the planar antenna is reduced by 39% compared with the original structure, and the perturbation moments are decreased by 52% at uniform speeds and by 39% at variable speeds.

The normal operation of spaceborne parabolic cylindrical reflector antennas under various operating conditions relies on maintaining the root mean square (RMS) of the reflector surface’s deformation within reasonable limits. In engineering practice, the designing of reinforced ribs is the primary way to control the RMS of the reflector surface. However, the layout and dimensions of reinforced ribs for many existing designs rely on the experience of the designer and lack a theoretical foundation. This leads to suboptimal layouts and dimensions in many designs, deviating from the optimal design. To address these concerns, this study proposes a comprehensive design approach that combines both topology optimization and parametric analysis. Optimization and parametric analysis were conducted for a large-sized spaceborne composite parabolic cylindrical reflector antenna. The layout and dimensions of the reinforced ribs were reconstructed based on the optimization results and parametric analysis. This study also obtained the influence of the height and thickness of the reinforced ribs on the RMS of the reflector surface. Subsequently, utilizing antenna temperature field simulations as thermal excitation inputs, finite element thermal distortion analyses were conducted for the reflector surfaces without reinforced ribs, with the original reinforced ribs designed based on empirical methods, and with optimized reinforced ribs. In comparison to the original design of the reinforced ribs, the optimized design, without an increase in the volume of the reinforced ribs, reduced the RMS of the reflector surface from 0.6025 mm to 0.5561 mm, resulting in an optimization ratio of 7.7%. Moreover, when compared to the reflector surface without reinforced ribs, the optimized design achieved a 17.9% reduction in RMS.